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R. Razavi (Podcasting)
Podcasting A podcast is a type of '''''digital media consisting of an episodic series of audio radio, video, PDF, or ePub files subscribed to and downloaded through web syndication or streamed online to a computer or mobile device. The word is a neologism derived from "broadcast" and "pod" from the success of the iPod, as podcasts are often listened to on portable media players. In the context of Apple devices, the term "Podcasts" refers to the audio and video version of podcasts, whereas the textual version of podcasts are classified under the app known as Newsstand.A list of all the audio or video files currently associated with a given series is maintained centrally on the distributor's server as a web feed, and the listener or viewer employs special client application software, known as a podcatcher, that can access this web feed, check it for updates, and download any new files in the series. This process can be automated so that new files are downloaded automatically, which may seem to the user as if the content is being broadcast or "pushed" to them. Files are stored locally on the user's computer or other device ready for offline use, giving simple and convenient access to the content. Podcasting contrasts with webcasting (Internet streaming), which generally isn't designed for offline listening to user-selected content.As discussed by Richard Berry, podcasting is both a converged medium bringing together audio, the web and portable media player, and a disruptive technology that has caused some in the radio business to reconsider some established practices and preconceptions about audiences, consumption, production and distribution. This idea of disruptiveness is largely because no one person owns the technology; it is free to listen and create content, which departs from the traditional model of 'gate-kept' media and production tools. It is very much a horizontal media form: producers are consumers and consumers become producers and engage in conversations with each other. Screencast A screencast is a digital recording of computer screen output, also known as a video screen capture, often containing audio narration. The term screencast compares with the related term screenshot; whereas screenshot is a picture of a computer screen, a screencast is essentially a movie of the changes over time that a user sees on a computer screen, enhanced with audio narration. Uses '' ''Screencasts can help demonstrate and teach the use of software features. Creating a screencast helps software developers show off their work. Educators may also use screencasts as another means of integrating technology into the curriculum. Students can record video and audio as they demonstrate the proper procedure to solve a problem on an interactive whiteboard.Screencasts are useful tools for ordinary software users as well: They help filing report bugs in which the screencasts take the place of potentially unclear written explanations; they help showing others how a given task is accomplished in a specific software environment.Organizers of seminars may choose to routinely record complete seminars and make them available to all attendees for future reference and/or sell these recordings to people who cannot afford the fee of the live seminar or do not have the time to attend it. This will generate an additional revenue stream for the organizers and makes the knowledge available to a broader audience.This strategy of recording seminars is already widely used in fields where using a simple video camera or audio recorder is sufficient to make a useful recording of a seminar. Computer-related seminars need high quality and easily readable recordings of screen contents which is usually not achieved by a video camera that records the desktop. HTTP Live Streaming '''HTTP' Live Streaming''' (also known as HLS) is an HTTP-based media streaming communications protocol implemented by Apple Inc. as part of their QuickTime and iOS software. It works by breaking the overall stream into a sequence of small HTTP-based file downloads, each download loading one short chunk of an overall potentially unbounded transport stream. As the stream is played, the client may select from a number of different alternate streams containing the same material encoded at a variety of data rates, allowing the streaming session to adapt to the available data rate. At the start of the streaming session, it downloads an extended M3U (m3u8) playlist containing the metadata for the various sub-streams which are available.Since its requests use only standard HTTP transactions, HTTP Live Streaming is capable of traversing any firewall or proxy server that lets through standard HTTP traffic, unlike UDP-based protocols such as RTP. This also allows content to be delivered over widely available CDNs.HLS also specifies a standard encryption mechanism using AES and a method of secure key distribution using HTTPS with either a device specific realm login or HTTP cookie which together provide a simple DRM system. Later versions of the protocol also provide for trick mode fast-forward and rewind and integration of subtitles. Uplynk has also added the AES scrambling and base-64 encoding of the DRM content key with a 128-bit device specific key for registered commercial devices together with a sequential initialization Vector for each chunk to their implementation of the standard. So the use of a DRM content key requires secret closed source code to obscure device specific information making a complete GNU General Public License product impossible to legally develop for the Linux-libre community.Apple has documented HTTP Live Streaming as an Internet-Draft (Individual Submission), the first stage in the process of submitting it to the IETF as an Informational Request For Comments. However, while Apple has submitted occasional minor updates to the draft, no additional steps appear to have been taken towards IETF standardization. From Wikipedia,the free encyclopedia '''